1. Field of the Invention
This invention relates to powders for compaction and sintering and, more particularly, to micron size powders having nano size reinforcements.
2. Description of the Related Art
Composite materials containing two different components are well known. Reinforced concrete provides a simple example. FIG. 1A illustrates a non-reinforced concrete beam 3. A load 6 will tend to deform the beam 3, inducing cracks 9 on the tension side 12, which can cause the beam 3 to fail.
FIG. 1B illustrates a reinforced concrete beam 18, which contains a steel reinforcing bar 21 on the tension side 12. The reinforcing bar 21 absorbs the tensile load on the tension side 12. The concrete itself, being high in compressive strength, absorbs the compressive load on the compression side 24.
The reinforced beam of FIG. 1B can carry a larger load than the non-reinforced beam of FIG. 1A by properly combining the desirable properties of two different materials, steel and concrete.
Similar principles of reinforcement have been applied to sintered materials. Studies exist where reinforcements of small whiskers or fibers of high tensile strength, having diameters in the range of several microns, have been incorporated into the sintered materials. Similarly, particulate reinforcements of micron size (1-100 microns) have been incorporated into matrix powder and sintered to obtain sintered composite body.
For example, titanium particulates, larger than 10 microns, have been mixed with carbon or boron fibers, also larger than 10 microns. The mixture is then compacted and subjected to a sintering process, wherein the carbon or boron reacts in situ with the titanium, to form precipitates of titanium carbide or titanium boride reinforcement.
It is known that nano grain size materials show unique properties such as mechanical, optical, electrical, and catalytical properties.
However, difficulty has been encountered in attempts to fabricate very small reinforcements, in the nanometer range, within a powder matrix in the micron range. Specifically, if the titanium micron powder of the example immediately above is mixed with titanium carbide particulates in the nanometer range, using ordinary agitation techniques, it is found that the carbide powder agglomerates together, forming islands, and does not become uniformly distributed throughout the titanium powder matrix.
FIG. 2 illustrates a specific example of non-uniformity. A micron size powder was mixed with a nano size powder, compacted and sintered. The dark islands indicate the titanium carbide produced by the nano powder, and the surrounding white regions indicate the titanium metallic regions.
What is needed is a system and method that overcomes one or more of the problems of the prior art, and that attains a more uniform distribution of nano size powders within a micron size matrix.